As a general rule, and I would recommend always reading the manufacturers product information sheets for the best info, any acid-based primer (aka, self-etching, wash primer, etc) should never have any polyester based product (body filler or primer) applied directly to it. It will NOT stick. Always topcoat wash primers with epoxy or urethane primer before applying fillers. Even after sanding, if there's even a little tiny area that's broken through and has bare metal or the edge of an etch primer showing, spot prime that area with something else before applying filler. It's that critical. Body and paint work is hard work and the materials are expensive. It's not worth the risk of having to do something over again simply for not following instructions.

 

I read the instructions. All 3 or 4 lines on the back of the rattle can. . Thanks for the heads up. So what do you suggest? Just go ahead and spray the epoxy over the etching primer, or should I just sandblast the primer back off before I get serious with the bodywork? No big deal to me either way. I was just following someone else's advice and threw it on there to cover the bare metal.

 

It depends on the primer. They make both cheap stuff and professional products in rattle cans, and I don't know what you used. If it's good stuff, you can apply an epoxy primer over it and you'll be fine. If it's a cheap drug store type, you'll want to make sure it's compatible with professional topcoatings (most are not) or remove it and start over. Remember this one rule, your final finish is going to be no better than your foundation. A cheap primer is no place to start.

 

I think I used about 4 cans total of that Rustoleum Etching Primer they sell at Autozone.

 

I'm not a chemist, so I can't say what will work with what in this case. You could check with the Rustoleum people, or your paint supplier for their recommendation. If it's questionable at all, I'd start over.

 

Way2fast1,
Undercoats are in 3 different categories: primer, surfacers and sealers.
Primers are designed to stick to bare substrates. That’s what you are saying you want to do.
Surfacers are to fill small imperfections and sand scratches.
Sealers seal out undercoats and provide improved adhesion for topcoats.
Many times companies will make products that combine several properties and will usually be advertised that way. IE. Primer-surfacer, primer-sealer etc.
I don’t usually put one brand ahead of others, but for coating bare metal that I will work on later I would definitely go with PPG products DP epoxy primers. The DP90LF is an excellent product for corrosion protection and adhesion, I have personally used it on bare metal for up to 3 years without rust starting back. It is offered in several colors, but the DP90LF is black and looks a lot like the factory primer and can be used on bare frames and top coated from there. It is very easy to spray, but as with any epoxy, mix up only enough that you are ready to use at one time.

 

The options change because the products evolve over time. Most of the professional painters that I know learned on one system and they stick with it forever...irregardless of how many "new and improved" products hit the market. If you were to talk to each of them individually you would get almost as many recommendations as there were painters...the only ones that would completely agree would be the ones using the same product line, and even that is no guarantee.
As a rule of thumb...anything that is catalyzed (has a hardener) should be compatable with any top coat. What many call "epoxy" is not actually epoxy in the true sense of the word, it is a catalyzed urethane product that has many of the properties of epoxy but is tailored to meet the needs of the automotive refinishing market. Since most basecoats are not catalyzed, then care must be taken to use a compatible clear coat. I have used House of Kolor UC-35 clear over many brands of basecoat and have never had a problem. I even sprayed it over freshly stained wooden doors on the entry to my neighbors house...wears like iron and stays glossy for years.
As for etching primer...that is old school technology. I use a product from SEM called MetaLock which is a primer/surfacer/sealer all in one (creativecars1 described this type of product in post 21). Use it straight up as a high build primer over bare metal or thin it partly for a surfacer or thin it to the limit for a sealer. Sprays on smooth, dries fast, sands easily, and is ultra durable. I have a core support that I built for my truck that has been sitting outside for over a year now with only a couple of coats of MetaLock on it...it still looks as good as the day I sprayed it. If you really want to know how good your metal prep/primer job is then take a DA with some 400 grit paper and sand through the primer until you expose the metal beneath. If the primer has good adhesion then you will see a very gradual transition from the shiny metal to the primer. If you look closely you should even be able to see the primer still holding on in the scatches. If the primer is not bonding correctly you will see a hard edge between the metal and the sanded primer...you may even see some flaking of the primer if the bond is really poor or the primer has not been applied correctly. Bare metal should only need a wipe down with wax and grease remover before applying the primer.
As for the rattle cans I avoid them at all cost. The paint in them has been thinned to the max and they are very expensive when compared with the paint you mix and spray yourself. In the old days Rustoleum used a fish oil based paint that was not compatible with automotive paints. Many people used it to coat bare metal and then were disappointed when they attempted to top coat it with real automotive paints. I am not sure how compatible Rustoleum is today but I still avoid it.

 

Excellent information in this thread!

 

Hopefully you have a moisture trap for your airline as well, nothing worse than water in you paint as you spray it on. Depends where you live temperature wise as well,as that can have an effect. Consider what paint catalists you will need - they are different depending on if you are using a baking oven or spraying and air drying at home.

Having painted my truck myself I can tell you there is a lot to consider but the satisfaction of having done it yourself is immense!! I'd suggest you buy a couple of good books on automotive painting before you leap in as it could save you a lot of extra work and expense if you get it wrong...

 

Subscribing so I can find it easier in the future. Good info

 

I read somewhere in the past about weld thru primers. Any opinions either way. chuck

 

Yet another good point that I need to know as well. I think I speak for a lot of us out there when I say I wish there was just a 100% fool-proof this-is-the-way-it's-done set of instructions. If the professionals can't stay up with all of the new technologies out there, those of us who are amateurs don't have a chance.

 

Here is an excellent must read; Perfect Paint Job

another one; Deviations from the perfect job

another one; Paint Gun Adjusting

and another one; http://www.spiuserforum.com/showthre...t-Commandments

Good luck, and let me know if any of these help.

 

Excellent! Thanks for sharing.

 

Thanks for all the great info. I certainly have lots to consider. I do have a good respirator, water and oil trap on the way along with some other supplies. Think I will stop by my local English color this weekend and see what they say as well!